The Comparative Pathology and Mouse Phenotyping Shared Resource (CPMPSR) provides expert, readily available and affordable experimental pathology support to investigators utilizing animal models to study human cancer. Formeriy known as the Mouse Phenotyping Shared Resource (established in 2001), it has been extensively reorganized since the recruitment in September 2008 of Krista La Perle, D.V.M., Ph.D., from Memorial Sloan Kettering Cancer Center. Dr. La Perie is a board-certified veterinary pathologist and NIH-funded, postdoctoral alumna of OSU's Department of Veterinary Biosciences (VBS). The shared resource name change reflects the diverse species of animals utilized in varied projects conducted by OSUCCC members that evaluate therapeutic efficacy, chemoprevention and safety of novel therapeutics in rodent and non-rodent xenograft and metastasis models, while continuing to emphasize the phenotypic characterization of newly generated genetically engineered mice. Under Dr. La Perie's direction and strong institutional support, the laboratory was relocated, technical support was expanded, and a second, dedicated comparative pathologist is being recruited. All of these improvements are designed to improve the quality of comparative pathology support provided to OSUCCC members and address concerns of the 2004 CCSG review. Continued services include comprehensive macroscopic and microscopic examinations of various species of laboratory animals, including genetically engineered mice. Clinical pathology testing including hematology, clinical chemistry and urinalyses performed previously by the OSU Veterinary Teaching Hospital Clinical Pathology Laboratory are now conducted in-house on newly acquired analyzers by a dedicated medical laboratory technologist. The CPMPSR also utilizes reference laboratories for novel tests not performed in-house. Radiography is performed by the CPMPSR to enhance morphologic evaluations on post-mortem specimens. The CPMPSR works closely on serial, ante-mortem imaging and pathology correlates with the OSUCCC Imaging Shared Resource to assist investigators who need the wide array of ante-mortem imaging modalities offered by the OSUCCC. Preparation of routine frozen and paraffin slides, tissue microarrays and special histochemical and immunohistochemical staining previously performed by the VBS Histology and Immunohistochemistry Core is now integrated with the CPMPSR. An extensive menu of immunohistochemical antibodies specifically for use on rodent tissues has been established. Tissue microarrays incorporating tumors from various mouse models of cancer have also been prepared. The CPMPSR provides a referral service to experienced scientists within the OSU research community providing expertise in animal model development, experimental design, optimal sample collection and data interpretation. The CPMPSR is utilized by all six OSUCCC Scientific Programs and OSUCCC members account for more than 60% of all users. The CPMPSR leverages extensive institutional support, and seeks only 25.6% support from CCSG funds. The service contributes critical support to high quality cancer relevant publications and the education and training of future cancer investigators.